The invention relates to a ventilation device for transmissions with a lubricant containing water, wherein the ventilation device is connected to the transmission housing via a line and has a pressure equalization opening leading to the environment.
In oil-lubricated transmissions there is a ventilation opening, which allows pressure equalization with the environment when the temperature in the transmission rises or falls due to operating conditions and which is usually equipped as a device with installations for retaining oil mist and for keeping away dirt from the environment.
WO 2007/098523 A1 discloses a lubricant containing water, which in addition to a high proportion of water contains an agent lowering the freezing point, such as glycol, and further additives and/or suspended matters. Further details as well as the advantages to be obtained with such a lubricant can be gathered from the above-mentioned publication.
DE 22 20 565 discloses a recirculating cooling system for oil-lubricated reduction transmissions. A fan recirculates air containing oil vapors from inside the transmission through a heat exchanger back into the transmission. The condensed oil is returned separately. There is no pressure equalization with the environment.
Water has a very low vapor pressure in comparison to lubricating oil, so that it evaporates easily. This leads to the fact that not only the amount of lubricant in the transmission becomes less and less, which soon results in the destruction of the transmission, but also the composition of the lubricant changes because the proportion of water becomes smaller and smaller.
Thus it is the object underlying the invention to remedy this disadvantage and to counteract the loss of water to the environment.